This application claims the benefit of the Chinese applications 01102824.6 and 01202946.7 both filed Jan. 8, 2001.
1. Field of the Invention
The invention relates to a paraffin removal unit, more particularly to an automatic paraffin removal unit.
2. Description of the Related Art
In oil exploitation, from a bottom hole to the ground, pressure, temperature of underground crude are gradually lowered, while the paraffin molecules in the crude gradually solidify, deposit on the inner wall of oil tubing and pumping rod, diameter of the oil tunnel is gradually contracted, even blocked, and crude output is reduced even stopped in production. In order to exploit the crude from the bottom hole freely, periodical paraffin removal must be performed for the oil tubing and pumping rod. Paraffin removal methods in prior art comprise: (1) Hot melt, high temperature heated crude oil being injected into the oil well from the ground, to meet the deposited paraffin although the method is prevailing but massive crude and energy should be consumed, and a set of dedicated equipment is needed, a specially-assigned person has to be in charge of management, thereby oil exploitation cost is increased; (2) Mechanical paraffin removal, multiple scrapes are mounted on the pumping rod to scrape off paraffin, since a plurality of scrapers are installed, effluent oil being obstructed, not only increased equipment cost, but also added the load of oil pump; (3) Strong magnetic anti-paraffin de position, a strong magnetic means for anti-paraffin deposition mounted at the paraffin deposited segment in oil well, carries out magnetic treatment to effluent oil by the magnetic field of a permanent magnet in the section, to modify the molecular structure of paraffin in the oil, delay paraffin deposition, however, the method is inefficient and is chiefly discarded; (4) Chemical paraffin removal, specially-made chemical solvent is injected into an oil tubing, melts the paraffin to achieve the purpose of paraffin removal, but the cost of the method is still high. The maximum defect of periodical paraffin removal is between the two removals, paraffin deposited on the wall of oil tubing and pumping rod gradually increases, so that flow through resistance of crude increased, load of the oil pump is enlarged, pump efficiency is lowered, and the cost is up. The invention patent application titled xe2x80x9cOil Well Pole-climbing Cleanerxe2x80x9d is disclosed on Jan. 6, 1993 in the China Patent Gazette, with the disclosed number of CN 1067703A. The technology has the following problems: first is the tooth-tips of gearing change of a tumbler mounted on a pressure pad spring produces serious scuffing to the pumping rod, and its strength is grievously injured; second is that the tooth-tips of short gear teeth on both sides of the tumbler are in the shape of a straight line, and in point contact with the inner wall of tubing, being poor in anti-collision, and are easily worn-out, resulted in serious scuffing to the inner wall of oil tubing, after the tumbler tooth-tips are worn-out, the scraper slides to and from at the original position, cannot move up and down, and lost the function of automatic paraffin removal; third is a washer must be mounted on every tubing joint, otherwise when the scraper is passing over the joint, under the action of rebound inertia force from the return spring, tooth-tip of the tumbler inserting into the entry of oil tubing being clutched, and lost the function of paraffin removal; since the tubing joint is cone-shaped, screw-in depth is affected by the screwing force and machining accuracy, caused the screw-in depth of each tube to be different, hence washers of different fabricated length are needed in adaptable, the operation is tedious and difficult and hard in implementation.
The present invention is made to solve the above mentioned problems and overcome the drawbacks in the prior art. Accordingly, an object of the present invention is to provide a paraffin removal unit having a reasonable structure, which is convenient in mounting and use, able to perform automatic running reliably, and has a prolonged service life.
The foregoing and other objects of the present invention are achieved by providing a paraffin removal unit, comprising: a scraper clamped on the pumping rod and the upper and lower commutators connected to both end of the tubing segment requiring paraffin removal from well head to the section having a temperature lower than the paraffin deposition temperature; the scraper comprises a scraper body, a tumbler, an arc spring leaf, and a return spring, three sheets of arc spring leaves are mounted on the upper and lower ends of the scraper body, their relative positions are staggered with 60 degrees, to completely remove the paraffin deposited on the pumping rod; on the circle of scraper body, over three rows of rectangular through-holes and I-shaped slots in staggered arrangement are opened, and screw cutting edges whose positions staggered in 60 degrees are located at both ends; round pits having staggered positions are located on both sides of the I-shaped slots, when the steel spacing balls mounted on the tumbler slip into the round pits, i.e. spacing for the tumbler is realized, inward notched grooves are located on upper and lower sections of the I-shaped slots, the return torque springs are mounted symmetrically in the grooves, enable the short tooth-tips of tumbler to be adjoined to the inner wall of oil tubing; in which a tumbler is mounted at the middle of I-shaped slot, the tooth-tips of short gear teeth on both sides of the tumbler are arc-shaped, whose radius of circular arc is approximate to the tubing radius, and the middle gear tooth on the tumbler has a round angle, to reduce scuffing to the inner wall of oil tubing, meanwhile the anti-collision ability of tooth-tips is enhanced.
The upper and lower commutators comprises a sleeve an open spacing ring, and a tower spring, in which the open spacing ring of the tumbler is mounted in the upper cone cannelure of the sleeve, the scraper is not allowed to pass over, the tower spring is inverted in the cone cannelure mounted at the lower section of the sleeve, and the tooth-tips are not worn-out to realize commutation of every tumbler.
In order to restrict the position of the tumbler when the return spring rebounds to free state, a through-hole is fabricated nearby the mounting hole of tumbler, a spacing spring is mounted in the hole, a steel spacing ring is mounted on each of both ends of the hole respectively, when the steel spacing ball slips into a round pit on both sides of I-shaped notch on the scraper, then the tumbler""s position is restricted. A sinkhole having a diameter larger then that of the mounting hole fabricated on an end of the mounting hole of tumbler can also be employed, a round spring is mounted in the sinkhole, and appropriate limitation is performed to the tumbler position or to add a pressed spring in tubing joint to limit inverted turn of the tip of tumbler.
In order to prolong the service life of paraffin removal unit, wear-resistant material being inlaid on an end of every sheet of arc spring leaf.
Since the invention improved the shape of middle and short teeth on both sides of the tumbler, scuffing to the tubing inner wall is avoided, anti-collision ability of the tumbler is enhanced, and its service life is prolonged, an end of arc spring leaf is inlaid with wear resistant material, thereby the service life is extended, since a member for restriction of the tumbler position is mounted, no washer is needed at the middle section of tubing joint on passing over the tubing joint into a next tubing, the scraper shall not be clutched; since tower springs are mounted in the upper, lower commutators of the invention, every commutator switches over smoothly, the scraper runs successfully up and down, multiple paraffin removals can be performed for oil tubing and pumping rod daily, crude is smoothly exploited and the pump efficiency is not lowered, high paraffin removal cost is saved, and distinct economic effect being achieved.